Software-Defined Networking:
The New Norm for Networks
ONF White Paper
April 13, 2012
ONF WHITE PAPER
Software-Defined Networking: The New Norm for Networks
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© Open Networking Foundation. All rights reserved.
Executive Summary
Traditional network architectures are ill-suited to meet the requirements of
today’s enterprises, carriers, and end users. Thanks to a broad industry
effort spearheaded by the Open Networking Foundation (ONF), Software-
Defined Networking (SDN) is transforming networking architecture.
In the SDN architecture, the control and data planes are decoupled,
network intelligence and state are logically centralized, and the underlying
network infrastructure is abstracted from the applications. As a result,
enterprises and carriers gain unprecedented programmability, automation,
and network control, enabling them to build highly scalable, flexible
networks that readily adapt to changing business needs.
The ONF is a non-profit industry consortium that is leading the advancement
of SDN and standardizing critical elements of the SDN architecture such
as the OpenFlow protocol, which structures communication between the
control and data planes of supported network devices. OpenFlow is the first
standard interface designed specifically for SDN, providing high-performance,
granular traffic control across multiple vendors’ network devices.
OpenFlow-based SDN is currently being rolled out in a variety of
networking devices and software, delivering substantial benefits to both
enterprises and carriers, including:
• Centralized management and control of networking devices from multiple
vendors;
• Improved automation and management by using common APIs to abstract
the underlying networking details from the orchestration and provisioning
systems and applications;
• Rapid innovation through the ability to deliver new network capabilities and
services without the need to configure individual devices or wait for vendor
releases;
Table of Contents
2 Executive Summary
3 The Need for a New Network Architecture
4 Limitations of Current Networking Technologies
7 Introducing Software-Defined Networking
8 Inside OpenFlow
10 Benefits of OpenFlow-Based Software-Defined Networks
12 Conclusion
ONF
OpenFlow
Why SDN?
What is SDN?
ONF WHITE PAPER
Software-Defined Networking: The New Norm for Networks
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© Open Networking Foundation. All rights reserved.
• Programmability by operators, enterprises, independent software vendors,
and users (not just equipment manufacturers) using common programming
environments, which gives all parties new opportunities to drive revenue
and differentiation;
• Increased network reliability and security as a result of centralized and
automated management of network devices, uniform policy enforcement,
and fewer configuration errors;
• More granular network control with the ability to apply comprehensive and
wide-ranging policies at the session, user, device, and application levels; and
• Better end-user experience as applications exploit centralized network
state information to seamlessly adapt network behavior to user needs.
SDN is a dynamic and flexible network architecture that protects existing
investments while future-proofing the network. With SDN, today’s static
network can evolve into an extensible service delivery platform capable of
responding rapidly to changing business, end-user, and market needs.
The Need for a New Network Architecture
The explosion of mobile devices and content, server virtualization, and
advent of cloud services are among the trends driving the networking
industry to reexamine traditional network architectures. Many conventional
networks are hierarchical, built with tiers of Ethernet switches arranged in
a tree structure. This design made sense when client-server computing
was dominant, but such a static architecture is ill-suited to the dynamic
computing and storage needs of today’s enterprise data centers,
campuses, and carrier environments. Some of the key computing trends
driving the need for a new network paradigm include:
• Changing traffic patterns: Within the enterprise data center, traffic
patterns have changed significantly. In contrast to client-server applications
where the bulk of the communication occurs between one client and
one server, today’s applications access different databases and servers,
creating a flurry of “east-west” machine-to-machine traffic before returning
data to the end user device in the classic “north-south” traffic pattern. At
the same time, users are changing network traffic patterns as they push
for access to corporate content and applications from any type of device
(including their own), connecting from anywhere, at any time. Finally, many
enterprise data centers managers are contemplating a utility computing
model, which might include a private cloud, public cloud, or some mix of
both, resulting in additional traffic across the wide area network.
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© Open Networking Foundation. All rights reserved.
• The “consumerization of IT”: Users are increasingly employing mobile
personal devices such as smartphones, tablets, and notebooks to access
the corporate network. IT is under pressure to accommodate these
personal devices in a fine-grained manner while protecting corporate data
and intellectual property and meeting compliance mandates.
• The rise of cloud services: Enterprises have enthusiastically embraced
both public and private cloud services, resulting in unprecedented growth
of these services. Enterprise business units now want the agility to access
applications, infrastructure, and other IT resources on demand and à la
carte. To add to the complexity, IT’s planning for cloud services must be
done in an environment of increased security, compliance, and auditing
requirements, along with business reorganizations, consolidations, and
mergers that can change assumptions overnight. Providing self-service
provisioning, whether in a private or public cloud, requires elastic scaling
of computing, storage, and network resources, ideally from a common
viewpoint and with a common suite of tools.
• “Big data” means more bandwidth: Handling today’s “big data” or mega
datasets requires massive parallel processing on thousands of servers, all
of which need direct connections to each other. The rise of mega datasets
is fueling a constant demand for additional network capacity in the data
center. Operators of hyperscale data center networks face the daunting
task of scaling the network to previously unimaginable size, maintaining
any-to-any connectivity without going broke.
Limitations of Current Networking Technologies
Meeting current market requirements is virtually impossible with traditional
network architectures. Faced with flat or reduced budgets, enterprise IT
departments are trying to squeeze the most from their networks using
device-level management tools and manual processes. Carriers face similar
challenges as demand for mobility and bandwidth explodes; profits are being
eroded by escalating capital equipment costs and flat or declining revenue.
Existing network architectures were not designed to meet the requirements
of today’s users, enterprises, and carriers; rather network designers are
constrained by the limitations of current networks, which include:
• Complexity that leads to stasis: Networking technology to date has
consisted largely of discrete sets of protocols designed to connect hosts
reliably over arbitrary distances, link speeds, and topologies. To meet
business and technical needs over the last few decades, the industry has
evolved networking protocols to deliver higher performance and reliability,
broader connectivity, and more stringent security.